Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. A typical orthopaedic prosthesis for the knee includes a tibial tray, a femoral component, and a polymer insert or bearing positioned between the tibial tray and the femoral component. The tibial tray may include a stem or post that is implanted into the surgically prepared proximal end of the tibia to provide stability. In some applications, a stem extension may be coupled to the stem of the tibial tray to increase the overall length of the stem.